Mine is a Mio (or something like that). It's not top of the range like the TomTom's, but it's got a decent sized screen and has free lifetime maps included. However I think they may not have allowed for memory for future maps, as since the last update it has developed a speach impediment which I am sure is due to them dropping certain sounds from it's vocabulary in order to make the updated maps fit on it. Luckily I'm finding it quite entertaining.
I had an old Binatone satnav years ago that I hacked and installed celebrity voice packs on to. Having Chubby Brown, Del Trotter etc. take you to holiday was quite ammusing. Unfortunately though I couldn't update any maps at all and it got to the point where even chubby was saying "A haven't got a f***ing clue where THAT is!"